It has been estimated that the human body is 90% bacteria. So, for every cell in your body, you have nine cells of bacteria living in and on your body. Most of these bacteria are in the GI tract. Not surprisingly, the health of the GI tract is paramount to health of the body overall. Thus, the health of the gastrointestinal system and the health of the immune system are vitally linked. When gut bacteria are balanced, the immune system is also balanced. But when it’s out of balance, so is the immune system. Physiological signs that the immune system is out of balance include food and seasonal allergies, chronic inflammation, chronic sinusitis, and colds that linger.

Several articles have appeared recently about efforts to better understand the interactions between the human immune system and the gastrointestinal tract. For the nutraceutical professional, it is important to understand the interrelationships between diet, nutritional status, the immune and gastrointestinal systems.

The Human Gastrointestinal & Immune Systems
Sheila Campbell, PhD, RD, commented that more than 20 years ago, her boss at a major medical foods company fixed on her with his hawk eye glance and opined in his cowboy twang, “The gastrointestinal tract (GI) isn’t just a flabby inner tube to shovel food through, ya know.” Genius! True, the GI tract is incredible. Sheila continued by pointing out that the GI systems does the following:

Produces and circulates eight liters of fluids daily;

Manufactures about a half-gallon of hydrochloric acid daily;

Protects itself by creating a fresh mucous coat every two weeks;

Synthesizes 22 digestive enzymes;

Makes five hormones;

Defies gravity—you can stand on your head while eating and food will still go to your stomach; Provides a nutrient absorptive area that, if spread out, covers the size of a tennis court.

Aside from these functions, the GI tract itself is an organ of the immune system. It houses 70% of the entire immune system in gut-associated lymphoid tissue (GALT). About 80% of plasma cells responsible for IgA antibody production reside in GALT. The presence of immune cells in the gut makes sense, considering that the GI tract opens to the external environment. Potentially pathogenic microbes have easy entry to the GI tract (Clinical and Experimental Immunology, 2008).

As much as three pounds of microbes—100 trillion bacteria—reside in the human gut. Optimally, most are beneficial rather than pathogenic.

It is to our benefit to maintain the community of microbes in the gut because a healthy balance of helpful microbes (probiotics) makes the digestive tract environment inhospitable to harmful microbes. Further, disrupting a normal, healthy balance of gut microbes is associated with developing or worsening of chronic conditions, including inflammatory bowel disease (IBD), obesity, autoimmune diseases, and allergies. All of these conditions are associated with immune dysfunction (i.e., chronic inflammation).

Today, experts say the gut microbiota (the organisms comprising the microbial community) are so important that, en masse, it is now considered a human organ, with its own functions, including intestinal cell gene expression.

The value of maintaining a healthy balance of gut microbiota helps explain the current interest in pre- and probiotics. Prebiotics are indigestible, fermentable fibers. Helpful gut microbiota (probiotics) metabolize prebiotics for energy, producing short chain fatty acids (SCFA) as byproducts. SCFA in turn, nourish cells of the colon, helping to maintain digestive tract integrity and function as a physical barrier to pathogens.

The Consumer Perspective
Research into consumers’ trust in dietary supplements indicates products addressing immune and gastrointestinal health are two of the top conditions viewed as safe and effective. The use of supplements for bone health is the only condition that rates higher in terms of consumer trust.

According to the 2016 Council for Responsible Nutrition (CRN) Consumer Survey, among U.S. adults who take supplements, 23% do so to address immune health issues and 17% for GI health. Primary consumer research suggests there is considerable overlap between these two consumer groups. Not only do they take supplements for both conditions, but they also use the supplements to address common immune-GI health issues. Consumers are becoming more aware of the interrelationship between the two systems.

What nutrients do consumers associate with immune health? The number one category has typically been antioxidants, but with the increasing awareness of pre- and probiotics, ingredients often associated with GI health have advanced in the immune health category. The list goes on to include digestive enzymes, individual vitamins (e.g., A, B complex, C, D, E, K) and omega-3s.

Marketing professionals should realize the importance of these physiological interrelationships and plan strategically to address a largely unmet consumer health need.

Gregory Stephens
Windrose Partners

Greg Stephens, RD, is president of Windrose Partners, a company serving clients in the the dietary supplement, functional food and natural product industries. Formerly vice president of strategic consulting with The Natural Marketing Institute (NMI) and Vice President of Sales and Marketing for Nurture, Inc (OatVantage), he has 25 years of specialized expertise in the nutritional and pharmaceutical industries. His prior experience includes a progressive series of senior management positions with Abbott Nutrition (Ross Products Division of Abbott Laboratories), including development of global nutrition strategies for disease-specific growth platforms and business development for Abbott’s medical foods portfolio. He can be reached at 267-432-2696; E-mail: gregstephens@windrosepartners.com

Sheila Campbell
Sheila Campbell, PhD, RD, has practiced in the field of clinical nutrition for more than 30 years, including 17 years with Ross Products Division of Abbott Laboratories. She has authored more than 70 publications on scientific, clinical and medical topics and has presented 60 domestic and international lectures on health-related topics. She can be reached at smcampbellphdrd@gmail.com.

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